Could 3 Body Problem's aliens exist? The science behind Netflix's new hit
REGINA BARBER: Just a heads up. This episode discusses the eight-part series 3 Body Problem, and it has spoilers. We also discuss war and death, so please take care while listening.
EMILY KWONG: You're listening to Short Wave, from NPR.
BARBER: Hey, Short Wavers, Regina Barber here. We've been in the midst of our weekly Space Camp series on Short Wave, but way before Space Camp, and actually, way before I ever studied the stars, I was a lover of science fiction. And one show that really satisfies my sci-fi craving is this Netflix series that begins with a space mystery. In it, the world's leading physicists begin dying, and physics itself seems to stop working. It was adapted from a bestselling book by Liu Cixin, translated by Ken Liu. And the first time Michael Wong encountered it, he says he was captivated by the plot, partly because of his background. He's an astrobiologist and studies planets, but partly because at the end of the day, he's just a huge science fiction lover, like me.
MICHAEL WONG: In a nutshell, the 3 Body Problem is basically the story of an alien invasion. The reason why the aliens are on their way to Earth is because they've evolved on a chaotic planet, one that experiences random climate extremes that causes civilizations to come and go. They basically collapse when the climate gets too hot or too cold.
BARBER: And they find present-day, stable Earth. Because way back in the 1970s, these aliens, called the San-Ti, made contact with a scientist. And she told them we existed, which, OK, there are no aliens in real life that we know of, but there is a lot of other stuff the book gets right, which is a big reason for Mike's love as a scientist and a sci-fi lover.
WONG: For instance, the San-Ti are traveling from a star system four light-years away. They're going at 1% the speed of light. And so it takes them 400 years to get from their homeworld to Earth. And that's a really important plot point. And it's also very realistic. There's no, like, warp speed or hyper speed.
BARBER: And the TV show has actually improved on the realism of the story in some ways, like how it highlighted all the collaboration across expertise and backgrounds that happens in science.
WONG: I love that the producers split one main character from the books into five different characters for the show. I think this is a great choice from just a production point of view, but for me, it's so important because this really fights against the lone genius stereotype in science, where you just have this, like, one solitary person who can, like, figure it out all on their own.
BARBER: And here's the thing. Even the name of the TV series and the first book is also a reference to real-life science. In physics, any object that feels forces is called a body. And the three-body problem is a real scientific concept, one that tries to explain the massively complicated orbits of three bodies in space. So today on the show, the 3 Body Problem, how science is portrayed in the novel and the hit TV show, what real-life scientists have to say about it. Plus, if aliens are out there, is it even ethical for us to try to contact them? I'm Regina Barber, and you're listening to Short Wave, the science podcast from NPR.
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BARBER: OK, Mike, before we go deeper into the series, let's start with some basic physics explainers here, OK? Because the orbit of two objects pulling on each other, it's fairly stable, right? So scientists have been able to predict those kinds of orbits very accurately for hundreds of years. I did this in, you know, undergrad. And this is the basic concept we need to understand before we get into this whole, like, three-body problem and how it complicates things.
WONG: Yeah, so any object with mass, you know, will exert a gravitational force on other objects in the vicinity. And so starting simply, just imagine two objects with mass, maybe, like, the Sun and the Earth, and they're both tugging on each other. The Sun's tug on the Earth, obviously, that makes the Earth swing around the Sun in a roughly circular orbit. That's, you know, why we have years, and we go around this beautiful star of ours.
BARBER: Right.
WONG: But the Earth also tugs a little bit on the Sun, and that causes the Sun to wobble just a little bit in space.
BARBER: Yeah, that's how we know that there's other planets around other stars because they wobble a little bit. I-- when I learned that, I was, like, blown away.
WONG: Exactly, yeah. We detect those little tiny wobbles of stars, and we infer, then, that there are planets that tug on those stars, even though we don't see those planets at all, or in most cases, we don't see those planets.
BARBER: So that's the two-body problem, like two objects pulling on one another, two bodies. Easy.
WONG: Right, so for the two-body problem, like between a planet and a star, you get very stable, very periodic, very regular solutions. But if you have three, you just throw one more gravitating object into the mix, all of a sudden, you don't get this beautiful, simple, general solution anymore. The system becomes chaotic. So even a tiny, little deviation can cause huge changes down the road.
BARBER: OK, and that chaos, that's what causes the three-body problem, which, like, is famously hard to solve.
WONG: So in astrophysics, the three-body problem describes the question of how you predict the motions of three mutually gravitating astronomical objects. Three bodies, all with gravitational pulls on each other, causes a chaotic system that can then be very difficult to predict the exact motion of.
BARBER: Right.
WONG: And so it makes it really difficult to predict the ultimate motions, you know, thousands, tens of thousands, millions of years in the future for three mutually gravitating objects. And so the only way to make this prediction is to integrate numerically, which means to go step by step, you know, inch forward in time, calculate the little bit of change in the positions and velocities of each of the three bodies incrementally, and then do that calculation over and over and over again. And actually, this relates to a scene that we saw in the Netflix series where one of the solutions in the video game that they're playing that was proposed by some other players involves basically building a human computer with these armies of people doing binary calculations.
BARBER: Yes.
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SPEAKER 1: Three-Body 1.0.
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WONG: And that's actually exactly what we have to do to solve the three-body problem, except we don't use human computers. We use supercomputers. But there's no, like, solution that you can just write pen and paper the way you can, you know, write the equation for a circular orbit or even an elliptical orbit around a star for a single planet. When you have three bodies, you have to do basically this grunt work of integrating bit by bit by bit to predict that future.
BARBER: Wait, OK, so, just to clarify, so for instance, when we have our own solar system, we have the Sun, and we have lots of bodies, right? We have Jupiter. We have, you know, Mars. We have Earth. We have eight planets. So how come that doesn't create, like, a nine-body problem?
WONG: Yeah, yeah, so, basically, you know, the Sun dominates the gravity of our star system. And so, you know, although Earth does get pulled by the other planets, like Jupiter and Saturn, it's very minute compared to what the gravity from the Sun is doing. So basically, think about the system of stars in the 3 Body Problem where you have three stars in a very chaotic orbit. If you imagined yourself as a planet around that triple star system, where the gravitational field at your planet is always changing because of the configurations of the three stars that you're orbiting, that's just going to wreak havoc on, you know, the amount of insulation that your planet is going to have, the amount of starlight that is being received. And that will definitely cause very chaotic climates.
BARBER: Yeah, I mean, I think a good example is, like, why we have seasons. We have this tilt on the Earth. That tilt makes it so you get more sunlight during the summer, and you get less during the winter. So that affects your climate. So just imagine not just more sunlight, but, like, the star's closer to you, and you're getting even more energy. Or you're getting none, and it must be just-- yeah, that's why they're leaving. [LAUGHS]
WONG: Right, exactly. And with three stars, you know, sometimes they're all up in the sky at the same time, and you just burn to a crisp. And yeah, that's going to create huge climatological changes.
BARBER: OK, so the premise is actually kind of realistic, which is awesome. And the alien civilization, which is fictional, comes from this star system that is real, Alpha Centauri.
WONG: Yeah, so there actually is a triple star system four light-years from Earth. And we call this star system the Alpha Centauri system. It's comprised of three stars, Alpha Centauri A, B, and C. But C is often called Proxima Centauri because it's actually the closest to us. And orbiting Proxima Centauri is a planet that we think might be habitable. That is, it's probably roughly the size and mass of the Earth. And it's in the Goldilocks zone around that star, meaning that it receives the right amount of starlight to potentially maintain liquid water on its surface. And it's just really amazing to think that, yeah, there's actually a habitable world that may have an alien civilization on it, for all we know, just four light-years away.
BARBER: So you're saying we don't know if it's habitable, and we don't really know too much about this exoplanet, right? Just, like, its location.
WONG: Yeah, that's right. So in order to figure out if it's habitable or, indeed, inhabited with life, we'll need to know more about the chemical makeup of this planet and know more about its surface conditions and understand if it has an atmosphere, because the atmosphere is what keeps Earth habitable. We don't know if this planet has an atmosphere. We don't know what its surface is made of, if it has oceans or continents, or it's just a bare rock. And we really don't have a good handle on what its chemistry is. This is because we're only inferring the existence of the planet through its gravitational influence on its host star. So in order--
BARBER: Yeah, we haven't imaged it or anything.
WONG: Exactly. We'll probably need to build a, you know, next generation telescope to be able to do this for terrestrial-sized worlds, rocky worlds the size of Earth, like Proxima Centauri B.
BARBER: Because we just don't have telescopes that can do that right now.
WONG: But could I just mention one more thing about Proxima Centauri B?
BARBER: Yes, absolutely.
WONG: I think it's very important to just make that distinction between the real-life Proxima Centauri B and the planet that is portrayed in the 3 Body Problem.
BARBER: Yeah.
WONG: Proxima Centauri B is not in a chaotic orbit. It's not going to, you know, leave Proxima Centauri and then go orbit the other two stars for a little bit and then, like, swing back out. You know, it's actually quite stable.
BARBER: So don't be scared. Like--
WONG: Right, exactly.
BARBER: --the San-Ti are not coming for us probably.
WONG: Yeah.
BARBER: OK. [LAUGHS] I mean, this is, like, a really good transition to, like, you know, people and society and ethics, right? Like, we're watching-- I'm watching this show and I'm thinking, like, should we reach out to other life forms outside of Earth, right? Like, what's the ethics of contacting aliens in the first place?
WONG: Oh, wow, yeah, this is a hotly debated topic in the astrobiology community, this idea of messaging extraterrestrial intelligence or [INAUDIBLE]--
BARBER: Wow.
WONG: --which is generally just projecting ourselves into the cosmos, being that sort of, like, beacon, saying, hey, we're here. Hey, we exist.
BARBER: Just like the show.
WONG: Yeah, exactly. Just like the show, right. And a lot of people get very worried about that because, again, we're a very young planetary civilization. Humankind has not been on planet Earth for that long, geologically speaking, evolutionarily speaking. And so the kinds of alien civilizations that might be listening to us are likely to be a lot older, and hence probably a lot more advanced than we are. So is letting a more advanced civilization know about our presence necessarily the best idea? You know, there's always that worry that we're inviting a bunch of existential risk. On the other hand, academics have argued that if there are super advanced extraterrestrial civilizations out there, they already know we're here. They can already observe our presence on planet Earth. Maybe messaging is not alerting them, you know, that we're here because they already know that we're here. And if they already know that we're here and they haven't conquered us yet, then maybe they're friendly.
BARBER: Maybe we're good. Maybe we're good.
WONG: [LAUGHS] Yeah.
BARBER: Yeah. Thank you so much, Mike, for talking to me about this, you know, this book, this series. I love sci-fi, and I know you do, too. So thank you.
WONG: Thanks so much for having me. This was a blast.
BARBER: Before we head out, a reminder that we'll be back tomorrow with our regular Short Wave and back Tuesday with our next installment of the Space Camp series, as the starship Short Wave-- that's you and me-- continues further and earlier into space time and deepens our understanding of the universe. And I have this sneak preview from one of our experts.
PRIYA NATARAJAN: Hi, Short Wave space cadets. It's Priya Natarajan, your admiral of the ocean of darkness. While you're out there in space, why not get your net out and fish for some dark matter to bring back to Earth? That way, we can study it and figure out what it is. I'll be eagerly awaiting your samples. As you know, this is a big unsolved question in cosmology.
BARBER: This episode was produced and fact-checked by Hannah Chinn. It was edited by our showrunner Rebecca Ramirez, and the engineer was Kwesi Li. Julia Carney is our Space Camp project manager. Beth Donovan is our senior director, and Collin Campbell is our senior vice president of podcasting strategy. Special thanks to our friends at the US Space and Rocket Center, home of Space Camp. I'm Regina Barber, and you're listening to Short Wave, from NPR.
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